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(No Model.)

G. E. FOSS.

PROGESS OF AND APPARATUS FOR DRYING LUMBER.

No. 414,204. I Patented Nov. 5. 1889.

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@WQT 61am UNITED STATES PATENT OFFICE.

GEORGE E. FOSS, OF ST. ALBANS, VERMONT, ASSIGNOR TO THE ST. ALBANSMANUFACTURING COMPANY, OF SAME PLACE.

PROCESS OF AND APPARATUS FOR DRYING LUMBER.

SPECIFICATION forming part of Letters Patent No. 414,204, dated November5, 1889.

Application filed fieptember 16, 1885. Serial No. 177,296- (No model.)

To all whom it may concern:

Be it known that I, GEORGE E. Foss, of St. Albans, in the county ofFranklin and State of Vermont, have invented a new and Improved Processof Drying Lumber and Apparatus Therefor, of which the following is aspecification.

This process and apparatus are designed for the drying and seasoning oflumber on a large scale. The lumber to be treated is placed on trucks orcars which travel on a track extending through a sweating and a dryingchamber. The lumber is first introduced into the sweating-chamber,wherein it I 5 is heated and steam is introduced and brought into directcontact with it, this treatment beingcontinued untilthewood is heatedthroughout and its pores are thoroughly opened. The lumber is thenpassed into one end of the drying-chamber, where it is again heated, andis subjected to the action of a current of air which absorbs themoisture from its surface. From tiine to time the charge of lumber ismoved forward in this chamber, and as it advances it encounters aircontinually less hot and drier, whereby as it becomes itself more drythe air which acts upon it is also drier, so that no moisture condensesupon the lumber, and accordingly when it reaches the discharge end ofthe chamber it is thoroughly dried. The air circulates through thedrying-chamber from the discharge to the receiving end thereof, beingdried by means of a condenser before entering the chamber. 3 5 Figure 1in the accompanying drawings shows my improved apparatus in longitudinalvertical section. Fig. 2 shows it in transverse vertical section cut onthe line 2 2 in Fig. 1.

Let A designate the sweating-chamber and E the drying-chamber, thelatter being a continuation of the former, and a railway-track beingextended through both. A sliding door B closes the entering end of thechamber A, 5 a second door separates the chamber from the chamber E, anda third door B closes the discharge end of the latter chamber. Thesedoors are shown as arranged to slide upwardly, being guided by verticalguides or ways 0 OJ- They are to be opened to admit and discharge thecars or trucks carrying the stacks of lumber.

The chambers A and E are heated by suitable means, preferably by a steamcoil or radiator G, which is arranged close above the floor of thechambers, and preferably between the track-rails, as shown in Fig. 2.The dry.- ing-chamber E is in free communication with the steam-coilstherein throughout the length thereof.

The truck-load of lumber is placed in the chamber A, and is heated bymeans of the coil G therein until it is raised uniformly to a sufficienttemperature, which should be in the neighborhood of 125 to 150Fahrenheit. When the wood has become sufficiently warmed, steam isturned into the chamber A by opening a valve (not shown) in the radiatorG, or in an independent steam-pipe, as may be preferred. The wood isthus moist- 7c ened and sweated for as long a time as may be necessaryto thoroughly open its pores. The proper duration varies with the kindof wood and with the size of the lumber, but is usually abouttwenty-four hours. After the lumber has been sufficiently steamed it ispassed immediately into the drying-chamber E. A circulation of air ismaintained through the drying-chamber from the lower discharge end H tothe upper receiving end I, and are- So turn-pipe J, extending from theend I to the end 11, completes the air-circuit. The circulation of theair in the direction indicated is induced by any suitable pneumaticappliance-such as a fan-blower K-located at any convenient point on thereturn-pipe J. As the air passes through the drying-chamber it absorbsmoisture from the lumber under treatment, and this moisture is extracted.in the return passage through the pipe J by return-pipe opens into apit extending below the floor of the drying-chamber.

In passing through the drying-chamber the air is gradually heated by thesteam-coils, so

that when the air escapes from the chamber it is at its highesttemperature. of the air in passing through the drying-chamber will comein direct contact with the steamcoils, and on being heated thereby willrise and mingle with the air passing through the central portions of thechamber, thus constantly raising the temperature of the same. The air isthus heated in passing through the drying-chamber. owing to the factthat the heating-coils are in free communication with the chamberthroughout the length thereof,

so that the longer air remains in the chamber,

the higher it will be heated. The temperature in the drying-chambershould not be permitted to exceed that of the steaming-chamber, since toattain the best results the lumber should not be subjected to any veryhigh degree of heat. The drying process takes usually at least five orsix times as long as the steaming process, and therefore thedrying-chamber should be made at least five or six times as long as thesteaming-chamber; hence where the steaming-chamber is made long enoughto receive one truck or car the drying-chamber is made long enough toreceive five or six or .more trucks or cars. As a result of thisarrangement the drying-chamber always contains lumber which is invarying conditions as to dryness, lumber moist throughout beingcontained at the ingress end, or next to the steaming-chamber, whereasthe lumber at the egress or discharge end is almost or quite completelydried. This arrangement is essential to the economical drying andseasoning of lumber in quantities by a continuous operation, and theapplication of the air-circulation and heating mechanism to thisapparatus is especially designed to most satisfactorily and economicallyaccomplish the best possible results. I prefer that the coil Gshallconsist of two headers with a series of parallel pipes passing from oneto the other, and that the steam' shall enter the header at the end H ofthe chamber E and pass simultaneously through the several pipes to theheader at the opposite end of the coil in the chamber A. I thenintroduce exhaust-steam to the coil, so that the portion of the latternearest the end H shall be much the hottest, in order to heat theincoming air, which has been cooled by the condenser, and also byradiation to maintain the nearly-dried lum ber at a sufficienttemperature to expel the residue of moisture therefrom. The steamremaining uncondensed after passing through the coil (or some of it)maybe advantageously used to moisten the lumber in the chamber A.

Hitherto lumber has been treated by being first subjected to a sweatingprocess in a steaming-chamber, and being then subjected to a longerdrying process in a proportionallylonger drying chamber 5 but thedifficulty hitherto has been that while in the drying chamber the lumberthroughout its treatment and in every portion of the chamber has beensubjected to an excessively-hot atmosphere.

More or less,

The air in these cases enters the dryingchamber at one end while hot andcirculates through the chamber, heating and parching the lumber, andbeing itself cooled as it approaches the moister lumber, so that as theneed for its absorbing moisture increases its absorptive powerdecreases.

In my present apparatus the air enters the chamber fresh from thecondenser very dry and comparatively cool, and it first comes in contactwith the driest lumber, and as it passes through the chamber it comessuccessively in contact with successively-moister lumber, and is itselfat the same time raised to a successively-higher temperature, being thuscontinually rendered more and more susceptible of absorbing the moisturefrom the lumber. ber in the different stages of moisture it is heatedgradually, and is thus rendered capable of absorbing a portion of themoisture from each successive truck-load of lumber. As the air is drawnpositively through the chamber by the fan-blower, its circulation can beso regulated that when it leaves the chamber and enters the return-pipeit will be thoroughly saturated with all the moisture it can retain atthe maximum temperature which it receives in the-chamber. apparatus canbe Worked to its entire capacity and great economy can be attained.Also,

owing to the air being drawn positively through the chamber in theproper direction, there are no adverse currents within the chamber, andconsequently the air never comes in contact with any lumber cooler thanitself upon which it could deposit moisture. The lumber is thussubmitted to a uniform treatment, and is dried gradually, beingsubjected, as it is from the time it enters the drying-chamber till itsdischarge therefrom, to an atmosphere which is gradually drier and drieras the lumber itself becomes drier and drier. The amount of drying whichthe lumber receives in different portions of the chamber and in equaltimes is therefore approximately uniform, which is conducive in thehighest degree to the attainment of the best results. Where lumber issubjected throughout the drying process to an atmosphere uniformly hotand with the conditions of capacity for absorbing moisture either leftto chance or disregarded altogether, an unequal drying and warping,checking, and hardened surfaces are the inevitable results, therebyrendering the lumber of inferior quality.

By the employment of the apparatus herein described the uniform dryingof the lumber Thus as the air meets the lum-' Thus the is very perfectlyattained and the quality of the lumber produced is most superior.

I claim as my invention- 1. In the process of drying lumber, passing thelumber from one end of the drying-chamber to the other during theprocess of drying and passing a current of air through said chamber inthe opposite direction, said airbeing introduced into said chambercomparatively cool and dry and being gradually heated to asuccessively-higher temperature during its passage through said chamber,substantially as set forth.

2. In the process of drying lumber, passing the lumber from one end ofthe drying-chamber t0 the other during the process of drying, passing acurrent of air through said chamber in the opposite direction, andheating said air during its progress through said chamber, whereby saidair, being introduced into said chamber comparatively cool and dry,becomes gradually heated to an increasinglyhigher temperature during itspassage through said chamber, substantially as set forth.

3. A closed drying-chamber into one end of which lumber in a moistcondition is introduced and from the other end of which the dried lumberis discharged, and heating appliances arranged to heat the contents ofsaid chamber, in combination with an airpipe which communicates at oneend with said drying-chamber at the ingress end thereof and at the otherend with said dryingchamber at the discharge end thereof, a condenserlocated in said pipe, and pneumatic appliances which establish a currentof air through said chamber from the discharge to the ingress endthereof, and thence backward 4. A closed steaming-chamber, a steam-in- 35 let pipe communicating therewith, a closed drying-chamber of a lengthexceeding that of the steaming-chamber, a sliding partition between saidsteaming and drying chambers,

doors or gates closing the open ends of said 40 chambers, and acontinuous track extending through said chambers, in'combination withheating appliances arranged in the lower portion of said drying-chamber,an air-pipe which communicates at its one end with the ingress 45 end ofsaid drying-chamber and at its other end with the discharge end of saidchamber, a condenser located in said pipe, and pneumatic applianceswhich establish a current of air through said chamber from the dis- 5ocharge to the ingress end thereof, and thence backward through said pipeand condenser, substantially as and for the purposes set forth.

In witness whereof I have hereunto signed my name in the presence of twosubscribing 5 5 witnesses.

GEO. E. FOSS. Witnesses:

ARTHUR C. FRASER, GEORGE H. FRASER.

